Why Is Anticoagulant (Blood-Thinning) Treatment Important in Atrial fibrillation?
- Faraz Afzal
- Oct 15
- 4 min read
Updated: Nov 10
When the heart beats in atrial fibrillation, the upper chambers (atria) lose their normal, coordinated contraction. As a result, blood doesn’t flow efficiently through the atria but tends to swirl and stagnate. When blood stands still, the risk of forming a blood clot increases.
If such a clot breaks loose, it can travel through the bloodstream to the brain and cause a stroke – one of the most serious complications of atrial fibrillation.A clot can also travel to the legs and block circulation there - a condition called peripheral embolism.
Preventing stroke and peripheral embolism is the main reason we prescribe anticoagulant therapy for atrial fibrillation.
Risk of Stroke in Atrial Fibrillation
The risk of stroke and peripheral embolism exists regardless of the type of atrial fibrillation you have – whether it’s paroxysmal (comes and goes), persistent, or permanent.
How high the risk is depends mainly on your CHA₂DS₂-VA score.On average:
Score 2 → about 2.5% annual stroke risk
Score 3 → about 3.7% annual stroke risk
Score 4 → about 5.2% annual stroke risk
Anticoagulation significantly reduces this risk — by about 65% — but it does not eliminate it completely.That’s why it’s important not only to treat atrial fibrillation once it occurs, but also to prevent it from developing in the first place.
How to prevent atrial fibrillation — and thereby prevent stroke — will be discussed in a future article.
Who Needs Anticoagulation? The CHADS-VA Score
Not everyone with atrial fibrillation has the same risk of stroke. To determine who benefits from anticoagulation, doctors use a tool called the CHADS-VA score.
It adds up your risk factors:
Letter | Meaning | Points |
C | Congestive heart failure | 1 |
H | Hypertension (high blood pressure) | 1 |
A | Age 65–74 years = 1 point, 75+ years = 2 points | 1–2 |
D | Diabetes | 1 |
S | Stroke or TIA (previous) | 2 |
V | Vascular disease (heart attack, peripheral artery disease) | 1 |
Rule of thumb: If your total is 1 point or higher, you usually need anticoagulation.
What Happened to CHA₂DS₂-VASc?
Previously, doctors used the CHA₂DS₂-VASc score, which also gave one point for female sex.However, newer studies show that women do not have a higher stroke risk simply because of gender – the risk comes from other factors.
Therefore, the new European guidelines (ESC 2024) have removed female sex from the calculation, and we now use CHADS-VA instead.
It’s important to note that much of the existing clinical research was done using the older CHA₂DS₂ or CHA₂DS₂-VASc scores, so you’ll still see these in scientific papers.
What About Aspirin (Albyl-E)? Isn’t That Enough?
Platelet inhibitors such as acetylsalicylic acid (Albyl-E) and clopidogrel (Plavix) are effective in preventing heart attacks but not sufficient to prevent stroke in atrial fibrillation.
These medications prevent platelets from clumping together and work well against clots forming in narrow arteries (as in heart attacks). However, anticoagulants act on a different level of the body’s clotting system and are the only effective treatment against the type of clots that form in the atria during atrial fibrillation.
However, anticoagulants also protect against heart attack and leg embolism.Therefore, most patients with atrial fibrillation can stop taking aspirin when starting anticoagulation — except in one important case:If you’ve had a heart attack, stent, or cardiovascular event within the past year, you may need both treatments for a limited time. This decision is made individually by your doctor.
Common anticoagulants include Eliquis, Xarelto, Pradaxa, Lixiana, and Marevan (warfarin).
What About Short Atrial Fibrillation Episodes Detected by a Smartwatch or Pacemaker?
Today, many people have smartwatches or pacemakers that can detect brief, symptom-free AF episodes.This is called subclinical atrial fibrillation. Do such short episodes require anticoagulation?
Two major studies have looked at this:
NOAH-AFNET 6: Found no clear benefit of anticoagulation for very short episodes detected by heart monitors.
ARTESIA: Included patients with slightly longer episodes of subclinical AF and found some benefit, but also an increased bleeding risk.
Current recommendation: If you have device-detected AF episodes lasting 6 minutes or more, you should be evaluated for anticoagulation just like in regular AF, using the CHA₂DS₂-VA score.Shorter episodes usually don’t require treatment but should be followed up by your doctor.
What About the Risk of Bleeding? The HAS-BLED Score
While anticoagulation reduces stroke risk, it also increases the chance of bleeding. To assess this, doctors use the HAS-BLED score:
Letter | Meaning |
H | High blood pressure (uncontrolled) |
A | Abnormal kidney or liver function |
S | Previous stroke |
B | Previous bleeding or tendency to bleed |
L | Labile INR (applies to warfarin) |
E | Elderly (over 65 years) |
D | Drugs (aspirin, NSAIDs) or alcohol use |
Important: HAS-BLED is not used to decide whether you should have treatment or not. It’s used to identify and manage risk factors (like high blood pressure) and to encourage careful monitoring. Even with a high HAS-BLED score, the benefits of anticoagulation often outweigh the risks if your CHADS-VA score indicates treatment.
Individual Assessment Is Always Important
Everything described above is based on clinical guidelines — general recommendations derived from large studies.But every patient is different:
If you’re frail or have limited life expectancy, the bleeding risk may outweigh the benefit.
If you have a high risk of falling, this must be considered.
Your personal preferences also matter and should be discussed with your doctor.
Other illnesses and your overall health must always be factored in.
The decision to start anticoagulation should always be made together with your doctor, based on your individual situation.
Summary
Atrial fibrillation increases stroke risk because blood stagnates in the atria
The CHADS-VA score helps determine who needs anticoagulation (≥1 point usually means treatment)
Blood thinners reduce stroke risk by ~65%, but don’t remove it completely
Aspirin or clopidogrel alone are not enough — real anticoagulation is needed
For device-detected AF, episodes ≥6 minutes should be evaluated for treatment
The HAS-BLED score helps identify and reduce bleeding risks
Individual evaluation is always crucial
Studies show that in Western countries, up to 30% of patients with atrial fibrillation are not adequately treated with anticoagulants.
If you have atrial fibrillation, talk to your cardiologist about your personal risk and treatment options.
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